<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>JS引入方式</title>
</head>
<body>

</body>
<script type="text/javascript">
    document.write("hello");//写到HTML
    console.log("heelo");//控制台
    var arr=[1,'hello',5]
    for (let i = 0; i < arr.length; i++) {
        document.write(arr[i]);
    }
   var str='asas'
    str.
    alert(arr[9]);//警告
</script>
</html>